<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form action="/mycal" method="post">
        <input type="text" name="x" value="{{ x }}">
        <select name="op">
            <option value="add" {% if op == 'add' %}selected{% endif %}>+</option>
            <option value="sub" {% if op == 'sub' %}selected{% endif %}>-</option>
            <option value="mul" {% if op == 'mul' %}selected{% endif %}>*</option>
            <option value="div" {% if op == 'div' %}selected{% endif %}>/</option>
        </select>
        <input type="text" name="y" value="{{ y }}"> =
        <span>{{ result }}</span>
        <div>
            <input type="submit" value="Starting Cal">
        </div>
    </form>

</body>
</html>